Remove useless debug write

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@10300 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/matroskaenc.c

@@ -147,7 +147,6 @@ static int mkv_write_header(AVFormatContext *s)
     }
     end_ebml_master(pb, tracks);
 
-    put_be64(pb, 0xdeadbeef);
     return 0;
 }